Rainwater reuse in urban areas: a mathematical model and a longterm modelling approach

Natural water resources are becoming increasingly limited due to global-scaleclimate change and water availability issues have become so severe that they must beaddressed. Given these issues, reuse of wastewater and rainwater provides a promisingway to cope with water shortages. This paper describes an investigation into the efficiencyof rainwater usage systems. A conceptual model was built to assess the behaviour ofrainwater tanks and their effectiveness in coping with water shortages. The study is basedon a long-term simulation (12 years) of different rainwater reuse tank schemes. Theassociated reductions in residential freshwater demand (water reuse efficiency) and wetweather runoff delivered to the sewer system (sewer discharge efficiency) were surveyed.The results clearly show that rainwater usage systems can significantly reduce drinkingwater consumption. The specific volumes required for the reuse of rainwater are high;however, for local scale application, the specific volumes necessary are comparable to thereservoir volumes already used to store freshwater resources during potable water shortage